A question has arisen again about the percentages I use when dyeing and how they relate to the tsps and tbsps found in many dye books. The answer is not simple. I have been converted to the metric system as it really makes dyeing so much easier for me. I can still be improvisational but always start out with concentrations of dye solution that are about 10%. Now like a lot of you , I started dyeing using Ann Johnston's wonderful Color By Accident. Ann uses tbsps and tsps in her recipes. I have taken several classes from Ann and we have agreed to disagree about our starting places!! She is very intuitive and very experienced and I am sure her tsps are pretty consistent over time while most of ours aren't!
However, for the sake of translation, and roughly right, 1 tbsp (15 gms) in 1/2 cup (120 ml) of water equals about a 12 % solution which could dye one yard very, very dark , 1 tsp about a 5-6 % which would give you medium/dark. Roughly dyes weigh in at about 5 gm/1 tsp.
So for my gradations (in volume terms), I would start with 2 tbsps of dye dissolved in 2 cups of water (this is for a gradation of 8 one yard pieces of fabric). I would put one cup of this solution into the first pot, add water to the remaining dye until it was 2 cups again, put one cup of that into the next pot, etc, etc until I am down to the 8th (and sometimes with the dark dyes I go 12 levels), watering it down by half each time. I use plastic 1 gallon good quality baggies (Hefty or Ziploc) for each yard of fabric. I reuse them until they get holes in them. I have a whole little process for this I developed over time so that it only takes about a 2 foot by 2 foot space to do this.
Now if you look at those dye charts from Pro Chem and Dharma, you will see that they talk about percentages as well. Most dyes are shown at roughly 3%. This translates in metric terms to: for every 100 gms of fiber (about a yard of pfd muslin), there are 3 gms of dye POWDER which is dissolved in some amount of water. Using my rough translater, this means that there is about 1/2 tsp of dye powder used for each one yard of fabric.
With dyes, it is the amount of dye and the amount of fabric that matter. Yes, the water does affect the final outcome a little (more water and the dye will bond to the water which is why you use salt in regular full immersion dyeing).
Now the reason I say roughly and I should say that in capital letters is that each of the dye powders weighs something different. Some are a lot heavier than others and over time, they put different amounts of fillers in so that the dye charts remain accurate (i.e., if for some reason a new manufacturer sends a batch of dyes that require less of a certain dye to dye the same amount of fabric, the distributors like Pro Chem will put in fillers so that they remain consistent over time from a weight standpoint -- I have noticed that in some of my "pure" blues). These fillers will cause changes in volume but because at least Pro Chem uses weight as the constant, the weights will remain pretty much the same thus giving you similar results while the volumes might change over time.
Just look at the jars when you order 1 lb of the different dyes -- different in terms of volume.
For me, it is just easier to use a little scale and weigh out 50 gms of dye and dissolve it in 500 ml of water which gives me a 10% concentration. 500 ml of water is just a bit over 2 cups of water. So if I want to dye a yard (100 mg) of fiber, I know that there are 10 mg of dye in 100 mls of water. So if I want a pretty dark - 5% - (darker than the Pro Chem charts), I will use 50 ml of that solution which will give me 5 gms of dye. I will add enough water to the fabric and dye so that the fabric can soak it all up.
So again:
1 tbsp = about 15 gms of dye
1 tsp = about 5 gms of dye
250 ml of water = a little over a cup of water
1000 ml (1 liter) = more than a quart
100 gms = about the wgt of 1 yard of dyers muslin
3% concentration = about 1/2 tsp of dye/1 yard of dyers muslin
1 lb = about 400 gm
1000 gms (kilogram) = 2.2 lbs
I probably lost most of you in the first sentence! I won't even go to converting liquid ml to oz! For the severely math impaired, stick to your totally improvisational methods! If you yearn to learn more about getting some predictability in your dyeing without several months of experiments or dye dogs, start out with some predictable dye strengths using weights and work from there! Some will never get frustrated by not being able to repeat a color they just love. I did get frustrated. And I still have fun throwing colors together to see what will happen! Just not all the time!
Compulsive person that I am, I also keep a chart with every fabric I have used to dye that lists the weight/yard. It varies incredibly! A yard of Kona cloth weigh in about 150 gms, pimatex at 120 gms, a yard of my linen/rayon mix 250 gms etc, etc. Naturally you need quite a bit more dye to get those heavier fabrics to dye to the value you get with the lighter fabrics. Some people might mistakenly think they just have a non pfd fabric because the same amount of dye they use on their dyers muslin doesn't give the same color on the heavier fabric. So I have just taken a lot of the guessing out of this whole process. I must say I was not converted to metric until I took Carol Soderlund's dye class though! I was getting some predictability but was still using tsp and tbsps and keeping extensive records of my experiments and results.
I will step down from my pedestal now and go back to dyeing my tans if there is anyone out there left reading this or anyone cares!